Quote Originally Posted by JAZZCNC View Post
Now I'm not into electronics so I don't know if when using a DC supply the drives still use their onboard Caps as extra smoothing.? . . my gut says they probably do.!
If they use the same input connections for DC as AC as I assume they do then the rectifier and capacitors must still be in the circuit.

One other thing to consider: If you add an additional rectifier and capacitors to make a DC supply for an AC driver you will also increase the inrush current to the transformer and increase the risk of trips. Adding more capacitance for the sake of it to any DC supply (making Neale's audio amp PSU instead of a motor driver one) will have the same effect.